Rollup merge of rust-lang#84374 - CDirkx:gitignore, r=Mark-Simulacrum

Clean up .gitignore

Categorizes entries in the `.gitignore` file.

Other changes:
- added `desktop.ini` (Windows equivalent of `.DS_Store`)
- removed `.hg/` and `.hgignore`

Author: GuillaumeGomez

.gitignore

@@ -5,53 +5,71 @@
 # created during manual debugging and many people like to clean up instead of
 # having git ignore such leftovers. You can use `.git/info/exclude` to
 # configure your local ignore list.
-# FIXME: This needs cleanup.
-*~
+
+## File system
+.DS_Store
+desktop.ini
+
+## Editor
 *.swp
 *.swo
-.#*
-.DS_Store
+Session.vim
 .cproject
-.hg/
-.hgignore
 .idea
 *.iml
-__pycache__/
-*.py[cod]
-*$py.class
+.vscode
 .project
+.favorites.json
 .settings/
+
+## Tool
 .valgrindrc
-.vscode
-.favorites.json
-/Makefile
-/build/
+.cargo
+# Included because it is part of the test case
+!/src/test/run-make/thumb-none-qemu/example/.cargo
+
+## Configuration
 /config.toml
-/dist/
+/Makefile
+config.mk
+config.stamp
+no_llvm_build
+
+## Build
 /dl/
 /doc/
 /inst/
 /llvm/
 /mingw-build/
-/src/tools/x/target
-# Created by default with `src/ci/docker/run.sh`:
-/obj/
+/build/
+/dist/
 /unicode-downloads
 /target
-# Generated by compiletest for incremental:
+/src/tools/x/target
+# Generated by compiletest for incremental
 /tmp/
+# Created by default with `src/ci/docker/run.sh`
+/obj/
+
+## Temporary files
+*~
+\#*
+\#*\#
+.#*
+
+## Tags
 tags
 tags.*
 TAGS
 TAGS.*
-\#*
-\#*\#
-config.mk
-config.stamp
-Session.vim
-.cargo
-!/src/test/run-make/thumb-none-qemu/example/.cargo
-no_llvm_build
+
+## Python
+__pycache__/
+*.py[cod]
+*$py.class
+
+## Node
 **node_modules
 **package-lock.json
+
 # Before adding new lines, see the comment at the top.